You may have been exercising and eating healthy, but the scale tells you different, clocking in at five more pounds than last week. Don’t worry, you can chalk it up to water weight, according to Raquel Dardik, M.D., gynecologist at NYU Langone Medical Center.

“Weight gain happens five days before your period, but you’ll be back to normal once you start,” she explains.

Pre-period water weight can range from half of a pound to 10 pounds, usually averaging around five for most women, Dardik explains.

Why?

The hormone progesterone—essential in the early stages of pregnancy—is to blame: when there’s no baby (aka when you get your period), these levels fall. As a side effect, each cell in your body retains an extra microscopic drop of water, Dardik explains.

While it doesn’t lead to weight change, bloating caused by gas can magnify the situation by making you feel a size bigger.

Maintain a healthy scale schedule to keep yourself in check.

Weigh yourself once a week, on the same day, at the same time, using the same scale. “The main thing is not to overdo it, because fluctuations in weight are common,” Dardik says..

You can combat these side effects the way you battle normal weight gain with exercise. Also, drinking a lot of water can to help get rid of water retention, says Dardik. Try to avoid fatty foods, alcohol, and salt, which triggers your body to hold onto water, says Dardik.

That extra weight that doesn’t disappear after your period could be caused by pre-period cravings that make you hungry for salty, greasy foods, and sweets—and that kind of weight will not come off after your period, Dardik warns.

So before you indulge simply because you're on your period, think about whether you want to be carrying that extra weight post-period.

Finally, check your weight, but don’t be paranoid about it.

Your best days are ahead of you, explains Dardik, as women usually feel at their peak in the first 7-10 days after their period.